Proposals for increasing organ donation are often rejected as incompatible with altruistic motivation on the part of donors. This paper questions, on conceptual grounds, whether most organ donors really are altruistic. If we distinguish between altruism and solidarity – a more restricted form of other-concern, limited to members of a particular group – then most organ donors exhibit solidarity, rather than altruism. If organ donation really must be altruistic, then we have reasons to worry about the motives of existing donors. (...) However, I argue that altruism is not necessary, because organ donation supplies important goods, whatever the motivation, and we can reject certain dubious motivations, such as financial profit, without insisting on altruism.Once solidaristic donation is accepted, certain reforms for increasing donation rates seem permissible. This paper considers two proposals. Firstly, it has been suggested that registered donors should receive priority for transplants. While this proposal appears based on a solidaristic norm of reciprocity, it is argued that such a scheme would be undesirable, since non-donors may contribute to society in other ways. The second proposal is that donors should be able to direct their organs towards recipients that they feel solidarity with. This is often held to be inconsistent with altruistic motivation, but most donation is not entirely undirected in the first place (for instance, donor organs usually go to co-nationals). While allowing directed donation would create a number of practical problems, such as preventing discrimination, there appears to be no reason in principle to reject it. (shrink)